FIGS. 4 to 6 describe a conventional electronic component sucking method used in, for example, an electronic component mounting apparatus that mounts an electronic component on a circuit substrate to suck the electronic component, during its mounting, to transfer it to its mounting position.
FIG. 4 shows a partial configuration of a general electronic component mounting apparatus for implementing the conventional electronic component sucking method. In FIG. 4, 11 is a rotating table that can be intermittently rotated wherein a plurality of rods 12 are equidistantly spaced on the periphery of the table so as to be elevated and lowered. A suction nozzle 13 that sucks an electronic component is disposed at the tip of each rod 12. Mechanical valves 14 for switching a vacuum circuit for each suction nozzle 13 on and off are disposed on the rotating table 11. In addition, a component supply table 15 is provided on which a plurality of component supply means 16 are disposed and which supplies a desired one of the electronic components in the component supply means to a component sucking position at which the component is sucked by the suction nozzle 13. A circuit substrate 17 on which electronic components are to be mounted is fixed onto an XY table 18, which is configured to allow a specified mounting position of the electronic component on the circuit substrate 17, which corresponds to the component sucking position by the suction nozzle 13.
As shown in FIG. 5, a cam for driving the suction nozzle 13 so as to elevate and lower it is rotated once (360.degree.) during a single component-sucking operation time (this is referred to as a "tact time"). During the former half of the operation, the rotating table 11 is intermittently rotated through a specified angle (this is referred to as an "index"), while the component supply table 15 is moved to place the desired electronic component at the component sucking position. During the latter half of the operation, the suction nozzle 13 is elevated and lowered to suck the electronic component.
The index period is set at a value of a period of time during which the suction nozzle 13 is in its elevation limit position or of an appropriate allowable period of time before or after the period of time of said elevation limit. In addition, a component supply table 15 movement enabled period is set based on the elevating and lowering operations of the suction nozzle 13. That is, the end point of the component supply table 15 movement enabled period is set at a point of time at which the component supply table 15 can be rotated without obstruction by the suction nozzle 13 after the nozzle 13 has been lowered until its tip contacts an electronic component 19 as shown in FIG. 6A. The starting point of the component supply table 15 movement enabled period is set at a point of time at which the suction nozzle 13 has been elevated up to the maximum height (h) of the electronic component 19 as shown in FIG. 6B.
Since, however, the conventional electronic component sucking method sets the component supply table 15 movement enabled period so as to have a specified interlock period based on the sucking condition of the electronic component 19 shown in FIGS. 6A and 6B, as shown in FIG. 5, the electronic component 19 is unlikely to interfere with a component housing table 20 however large an electronic component 19 is sucked, but the component supply table 15 movement enabled period is set relatively shorter.
As a result, the component supply table 15 must be moved over a long distance for positioning, and the tact time must be set at a large value if the time required by the table to move does not fall within the component supply table 15 movement enabled period. This reduces the working efficiency in the overall electronic component mounting process.